Systems and methods using single antenna for multiple resonant frequency ranges

ABSTRACT

A radio frequency device utilizing an antenna having a single antenna structure resonant on multiple resonant frequency ranges. The antenna can be configured to operate within multiple frequency ranges for communication according to respective protocols associated with the respective frequency ranges.

RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 12/123,826, filed May 20, 2008, assigned U.S. Pat.App. Pub. No. 2009/0289771 and entitled “RFID Device Using SingleAntenna for Multiple Resonant Frequency Ranges”, the entire disclosureof which is hereby incorporated herein by reference.

BACKGROUND

The present invention relates to a radio frequency identification (RFID)device using a single antenna for multiple resonant frequency ranges.RFID is a technology that incorporates the use of electromagnetic orelectrostatic coupling in the radio frequency (RF) portion of theelectromagnetic spectrum to uniquely identify and communicate with adevice attached to an object, animal, or person. With RFID, theelectromagnetic or electrostatic coupling in the RF portion of theelectromagnetic spectrum is used to transmit signals.

A typical RFID system includes a reader (interrogator) and a pluralityof tags. A reader includes an antenna and a transceiver, and transmits aradio frequency signal to a tag to initiate a response from the tag. Thetag (RFID device) contains an antenna, circuitry, and information to betransmitted to the reader. The tag antenna enables the circuitry totransmit its information to the interrogator, which converts the radiowaves reflected back from the RFID device into digital information thatcan then be passed on to computers that can analyze the data.

Conventional RFID devices are typically designed for use in a particularfrequency range, and according to a single communication protocol.Modifying the RFID devices to operate in additional frequency ranges,and with additional communication protocols, requires significant andcostly modifications.

In current EPCglobal® passive device architecture, the amount of timethat an RFID device can receive and transmit data per session islimited, due to the minimal amount of charge that the RFID passivedevice can store. In addition, the communication link betweeninterrogator and RFID device in current RFID systems is limited in rangedue to constraint distance parameters of powering the RFID device.

SUMMARY OF THE DESCRIPTION

In one aspect, the present disclosure includes a radio frequency deviceutilizing an antenna having a single antenna structure resonant onmultiple resonant frequency ranges. The antenna can be configured tooperate within multiple frequency ranges for communication according torespective protocols associated with the respective frequency ranges.

In another aspect, the present disclosure provides a radio frequencyidentification (RFID) device using a single antenna for multipleresonant frequency ranges.

For example, an embodiment of the invention features an RFID system thatincludes an RFID interrogator having an interrogator antenna configuredto operate within multiple frequency ranges. The system also includes anRFID device having an RFID circuit, and a device antenna coupled to theRFID circuit. The RFID device antenna can be configured to operatewithin multiple frequency ranges that match at least those of theinterrogator antenna(s) for communicating with the RFID interrogatoraccording to respective protocols associated with each respectivefrequency range.

In another aspect, an embodiment of the invention features an RFIDdevice including an RFID circuit, and an antenna coupled to the RFIDcircuit. The antenna can be configured to operate within multiplefrequency ranges for communicating with at least one RFID interrogator,according to respective protocols associated with each respectivefrequency range.

In another aspect, an embodiment the invention provides a method thatincludes 1) receiving radio frequency (RF) signals having differentfrequency ranges on an antenna coupled to an RFID device and tuned tothe different frequency ranges, 2) selecting protocols, such that eachprotocol is associated with only one of the frequency ranges of thereceived signals, and 3) processing the received signals according tothe protocols associated with the frequency ranges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an RFID system linked to a network.

FIG. 2 is a block diagram of an exemplary RFID system.

FIG. 3 is a block diagram of an exemplary RFID device.

FIG. 4 is a block diagram of an exemplary RFID device antenna.

FIG. 5A is a graphical representation of primary and secondary resonantfrequencies of an exemplary RFID device antenna.

FIG. 5B is a block diagram of an exemplary RFID device.

FIG. 6 is a block diagram of an exemplary RFID device.

FIG. 7 is a block diagram of an exemplary RFID device.

FIG. 8 is a flow diagram.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following description and drawings are illustrative and are not tobe construed as limiting. Numerous specific details are described toprovide a thorough understanding. However, in certain instances, wellknown or conventional details are not described in order to avoidobscuring the description. References to one or an embodiment in thepresent disclosure are not necessarily references to the sameembodiment; and, such references mean at least one.

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, design and manufacture companies may refer to a component bydifferent names. This disclosure does not intend to distinguish betweencomponents that differ in name but not in function.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” Also, theterm “couple” or “couples” is intended to mean an indirect or directconnection. Thus, if a first device couples to a second device, thatconnection may be through a direct connection or through an indirectconnection via other intermediate devices and connections. Moreover, theterm “system” is understood to include “one or more components” combinedtogether. Thus, a system can include an “entire system,” “subsystems”within a system, a radio frequency identification (RFID) tag, a readercircuit, or any other devices including one or more components.

In general, various embodiments of the present invention configure RFIDdevices with single antenna structures, for instance, multiband resonantantennas that are designed to operate at multiple carrier frequencyranges. A different communication protocol is utilized with eachfrequency range, and power can be received by RFID devices over multiplefrequency ranges.

FIG. 1 illustrates an exemplary RFID system 10 that includes a computer3 coupled to a network 2 and to an RFID interrogator 4. The RFIDinterrogator 4, which may sometimes be referred to as an RFID reader,includes a processor 5, a transceiver 6, a memory 7, a power supply 8,and an antenna 9. The RFID interrogator 4 is programmable and performstransmitting and receiving functions with the transceiver 6 and antenna9. Alternatively, multiple antennas may be connected to transmitters andreceivers. Through antenna 9, the RFID interrogator 4 can communicatewith one or more RFID devices 11 that are within communication range ofthe RFID interrogator 4. Data downloaded from an RFID device 11 can bestored in memory 7, or transferred by the processor 5 to computer 3.Thereafter, this transferred data can be further processed ordistributed to network 2.

The exemplary RFID device 11 includes device antenna 16 and RFID circuit17. The RFID circuit 17 can include a transceiver 12, a processor 13,memory 14, and depending on whether or not RFID device 11 is active,semi-active or passive, a battery 15. Any RF interrogation signal 18transmitted by the RFID interrogator 4 to the RFID device 11 is receivedby the antenna 16, and passed to transceiver 12 in RFID circuit 17. Whentriggered by the transceiver 12, processor 13 fetches the data (e.g.,time stamp, unique RFID code, and so forth) from memory 14 and transmitsa return signal 19 through antenna 16 to RFID interrogator 4, asmultiplexed data packets from transceiver 12.

As shown in FIG. 2, in an exemplary system 20, the RFID interrogator 4can be configured with antenna 9 that is designed to operate withinmultiple frequency ranges. Antenna 9 can be a multiband resonantantenna. Another RFID interrogator 25 may be configured with multipleantennas 21, 26 that can be tuned to different respective frequencies orfrequency ranges. For example, antenna 21 may operate in a 100 MHz widefrequency range centered at 900 MHz, and antenna 26 may operate in a 100MHz wide frequency range centered at 2.45 GHz.

The RFID device 11 can be configured with an antenna 16, such as amultiband resonant antenna, that is designed to operate at multiplefrequency ranges. Some antenna designs have a primary resonance andsecondary resonances, which enable the use of one antenna 16 formultiple carrier frequencies. Another option is to implement antenna 16as a single antenna structure, such as a patch antenna array, whichincludes multiple antennas and is resonant on multiple frequency ranges.A single antenna is desirable where space and antenna size are limited.The antenna 16 on device 11 is coupled to the RFID circuit 17, and tunedto frequencies or frequency ranges that match at least those of thecorresponding antennas 9, 21, 26 on RFID interrogators 4, 25. Forexample, antenna 16 on RFID device 11 may operate in a 100 MHz widefrequency range centered at 900 MHz to correspond to antenna 21 on RFIDinterrogator 25, and antenna 16 on device 11 may also operate in a 100MHz wide frequency range centered at 2.45 GHz to correspond with antenna26 on RFID interrogator 25. Such a configuration allows antenna 16 toreceive multiple signals 18, 23, 27 from the antennas 9, 21, 26 on RFIDinterrogators 4, 25, and to respond by transmitting signals 19, 24 onrespective frequency ranges that match those of antennas 9, 21, 26.

Referring to FIG. 3, device antenna 16 is connected to the RFID circuit17, which may include a respective transceiver 12 and a power supply 15.It should be noted that in place of transceiver 12, receivers such as adiode detectors and transmitters can be substituted and coupled toantenna 16. RFID processing circuitry 33 is coupled to the transceiver12 and power supply 15, and processes a signal according to respectiveprotocols.

Referring to FIG. 4, in an embodiment, a multiband (two-band) resonantantenna 40 can be constructed by coupling filter circuits 42, 43 (traps)to antenna 16. Filter circuit 42 includes inductor 45 connected inparallel with capacitor 46. Likewise, filter circuit 43 includesinductor 47 connected in parallel with capacitor 48. The value ofinductors 45, 47 and capacitors 46, 48 are selected depending on theexpected resonant frequency at which antenna 40 is to operate. Theresonant frequency (or trapping frequency) of the filter circuits 42, 43can be calculated by one divided by the square root of the product ofthe inductor times the capacitor (1/square root (L*C)). Antenna 16 canbe a dipole antenna having a feedpoint 44. The two-band resonant antenna40 can be constructed with off-the-shelf components, or fabricated usingmicrostrip, stripline, copper etching on PC boards, films, etc.

It should be noted that although dipole antennas are specificallydepicted in the figures, other antennas are possible, such as logperiodic dipole array, triband Yagi antennas, multiple parallel antennasjoined at a common feedpoint (dipoles, patches, etc.), multiple antennasconnected serially, and quarter wave dipoles, monopoles and whips.

FIG. 5A shows a graphical representation 50 of two resonances, a primary51 and secondary 52, which may be used to construct a multiband resonantantenna without the use of filter circuits 42, 43 in each arm of thedipole antenna 16. The secondary resonance 52 is usually not verypronounced, typically resulting in less than optimal performance at thesecondary (higher) frequency. However, this antenna design may be usefulwhere space is at a premium.

FIG. 5B shows an embodiment of the antenna graphically represented inFIG. 5A. Specifically, antenna 16 is coupled to two external filtercircuits 42, 43. Filter circuit 42 may pertain to resonant frequency 51,and filter circuit 43 may pertain to resonant frequency 52. The filtercircuits 42, 43 and antenna 16 are coupled to one or more RFID circuits17 on RFID device 11. As discussed above, the RFID circuits 17 mayinclude a power supply 15, receivers/transceivers 13, and a processor13.

FIG. 6 shows an exemplary RFID device 11 configured with the two-bandantenna structure 40 coupled to two additional respective filtercircuits 61 and 62. Power supplies 15, transceivers 13, and additionalcircuitry 33 may be attached to the filter circuit outputs 63, 64 onRFID circuit 17, and configured to operate simultaneously or one at atime. Matching circuits or components may also be added. Multipleprotocols, each carried at a different frequency, can be usedsimultaneously by connecting the appropriate protocol processingcircuitry 33 in RFID circuit 17 to each filter circuit output 63, 64.Two different protocols can be used by connecting the appropriateprocessor 13, transceiver 13, (and even power supply 15) circuitry tothe respective outputs 63, 64 of filter circuits 61, 62.

FIG. 7 shows exemplary RFID device 11 configured as a two frequencysystem in which one output 63 is used as a power supply, and the otheroutput 64 is used for receiving, transmitting, and processing signals.In particular, RFID device 11 includes the two-band antenna structure 40that is coupled to the two filter circuits 61 and 62. The output 63 offilter circuit 61 is connected to the RFID circuit 17 and used as apower supply. Specifically, a diode 72 is connected to output 63 andused as a half-wave rectifier to generate direct current (dc) voltagefor powering processor 13 and the RFID circuit 17. A filtering capacitor73 is coupled to the diode 72 to smooth out the dc voltage signal. Theoutput 64 of filter circuit 62 is also connected to RFID circuit 17.Incoming signals from filter circuit 62 are passed through diode 74 andfiltering capacitor 75 to the processor 13, which processes the receivedsignals according to a protocol associated with the frequency range ofthe received signal. RFID circuit 17 can also include an automatedvoltage control 71 for modulating the frequency on which the processeddata is to be transmitted.

System 20 can also be configured to utilize a different communicationprotocol (e.g., EPCglobal® protocol, EPC HF Class 1, EPC UHF Class 0,EPC UHF Class 1, EPC UHF Class 1 Gen 2) on each respective frequencyrange. Such a configuration permits the RFID interrogators 4, 25 tocommunicate with RFID device 11 simultaneously or serially over eachrespective frequency range. Using a different protocol on each frequencyrange also enables multiple RFID interrogators to communicatesimultaneously or serially at the different frequency ranges with thesame RFID device 11. More specifically, using multiple protocols enablesa single RFID device 11 to perform different functions. For example, anEPC UHF Class 1 protocol may be used by RFID device 11 foridentification of a hospital patient, and the same RFID device 11 usingan entirely different protocol (e.g., EPC HF Class 1) on a differentfrequency range can be used for communicating with hospital equipment,monitoring patient data, or communicating with a nurse station to reportpatient status at a greater distance.

As a further example, tuning or selecting antenna 9 on RFID interrogator4 and antenna 16 on the RFID device 11 to operate within a frequencyrange centered at 900 MHz, establishes a first communication linkbetween the RFID interrogator 4 and RFID device 11. Similarly, tuningantenna 9 on RFID interrogator 4 and antenna 16 on the RFID device 11 toalso operate within a frequency range centered at 2.45 GHz, establishesa second communication link between the RFID interrogator 4 and the RFIDdevice 11. The 900 MHz frequency range can be used as a carrier forcommunications according to a first protocol, and the 2.45 GHz frequencyrange can be used as a carrier for communications according to a secondprotocol. The RFID interrogator 4 and device 11 can communicatesimultaneously or serially over the two frequency ranges.

In another embodiment, the first frequency range may be used to providepower from the RFID interrogator 4 to the RFID device 11, and the secondfrequency range may be used for communication according to a particularprotocol. Powering the passive device 11 on the first frequency range,while simultaneously communicating over the second frequency range, hasthe advantage of enabling the device 11 to stay energized longer, toreceive or transmit more data per session and to extend processing time.The device 11 can also be configured to receive power from the RFIDinterrogators 4, 25 at multiple frequency ranges.

The powering of the RFID device 11, as opposed to commands or data sentto and from the RFID device 11, is typically a range-limiting factor inthe communications link between RFID interrogators 4, 25 and RFID device11. This is primarily due to free-space path loss, which tends toincrease with frequency. Free-space path loss is the loss in signalstrength of an electromagnetic wave that results from a line-of-sightpath through free space, with no obstacles nearby to cause reflection ordiffraction. Free-space power loss is proportional to the square of thedistance between the transmitter and receiver, and also proportional tothe square of the frequency of the radio signal. Therefore, whenselecting a frequency range to power the device 11, it can beadvantageous to utilize the lowest available frequency range to minimizethe effects of free-space path loss and to extend the range of thedevice 11. Data can be sent at a higher frequency, which tends tobalance the communication link.

In designing and implementing the antennas and system 20, frequencyranges are selected that are non-harmonic, non-integer multiple ornon-integer-fraction frequencies relative to the other selectedfrequency ranges. For example, if a first frequency range is centered at900 MHz, a subsequent frequency range should not be selected at 1800 MHz(the first harmonic of the first range). An advantage is if multipathinterference exists at the first frequency range, such interferencewould be very unlikely at the second frequency range. Using thisconfiguration, reliability and range can be improved by using redundantpower transmissions at multiple frequency ranges, either simultaneouslyor multiplexed one at a time.

In embodiments, the RFID device 11 with antenna can be implemented aspart of rigid (e.g., substrate-based) or flexible (e.g., RFID label)configuration. Depending on the application, printed or etched layouttechniques including stripline, microstrip, organic or polymersemiconductors can be utilized for fabricating planar components orcomponents on substrates that may be rigid or flexible.

FIG. 8 illustrates a method of operation 80 of an RFID device that is inaccordance with an embodiment of the present invention. The method (80)starts (81) by receiving radio frequency (RF) signals (82) havingdifferent frequency ranges on an antenna tuned to the differentfrequency ranges. Once the signals are received, protocols are selected(83) so that each protocol is associated with only one of the frequencyranges of the received signals. The method (80) then processes (84) thereceived signals according to the protocols associated with thefrequency ranges. Method (80) can then either end (85), or ifimplemented in an automated system e.g., firmware, the method (80) canproceed to step (82) and continue to repeat.

In this description, various functions and operations may be describedas being performed by or caused by software code to simplifydescription. However, those skilled in the art will recognize what ismeant by such expressions is that the functions result from execution ofthe code by a processor, such as a microprocessor. Alternatively, or incombination, the functions and operations can be implemented usingspecial purpose circuitry, with or without software instructions, suchas using Application-Specific Integrated Circuit (ASIC) orField-Programmable Gate Array (FPGA). Embodiments can be implementedusing hardwired circuitry without software instructions, or incombination with software instructions. Thus, the techniques are limitedneither to any specific combination of hardware circuitry and software,nor to any particular source for the instructions executed by the dataprocessing system.

While some embodiments can be implemented in fully functioning computersand computer systems, various embodiments are capable of beingdistributed as a computing product in a variety of forms and are capableof being applied regardless of the particular type of machine orcomputer-readable media used to actually effect the distribution.

At least some aspects disclosed can be embodied, at least in part, insoftware. That is, the techniques may be carried out in a computersystem or other data processing system in response to its processor,such as a microprocessor, executing sequences of instructions containedin a memory, such as ROM, volatile RAM, non-volatile memory, cache or aremote storage device.

Routines executed to implement the embodiments may be implemented aspart of an operating system or a specific application, component,program, object, module or sequence of instructions referred to as“computer programs.” The computer programs typically comprise one ormore instructions set at various times in various memory and storagedevices in a computer, and that, when read and executed by one or moreprocessors in a computer, cause the computer to perform operationsnecessary to execute elements involving the various aspects.

A machine readable medium can be used to store software and data whichwhen executed by a data processing system causes the system to performvarious methods. The executable software and data may be stored invarious places including for example ROM, volatile RAM, non-volatilememory and/or cache. Portions of this software and/or data may be storedin any one of these storage devices. Further, the data and instructionscan be obtained from centralized servers or peer to peer networks.Different portions of the data and instructions can be obtained fromdifferent centralized servers and/or peer to peer networks at differenttimes and in different communication sessions or in a same communicationsession. The data and instructions can be obtained in entirety prior tothe execution of the applications. Alternatively, portions of the dataand instructions can be obtained dynamically, just in time, when neededfor execution. Thus, it is not required that the data and instructionsbe on a machine readable medium in entirety at a particular instance oftime.

Examples of computer-readable media include but are not limited torecordable and non-recordable type media such as volatile andnon-volatile memory devices, read only memory (ROM), random accessmemory (RAM), flash memory devices, floppy and other removable disks,magnetic disk storage media, optical storage media (e.g., Compact DiskRead-Only Memory (CD ROMS), Digital Versatile Disks (DVDs), etc.), amongothers. The instructions may be embodied in digital and analogcommunication links for electrical, optical, acoustical or other formsof propagated signals, such as carrier waves, infrared signals, digitalsignals, etc.

In general, a machine readable medium includes any mechanism thatprovides (i.e., stores and/or transmits) information in a formaccessible by a machine (e.g., a computer, network device, personaldigital assistant, manufacturing tool, any device with a set of one ormore processors, etc.).

In various embodiments, hardwired circuitry may be used in combinationwith software instructions to implement the techniques. Thus, thetechniques are neither limited to any specific combination of hardwarecircuitry and software nor to any particular source for the instructionsexecuted by the data processing system.

Although some of the drawings illustrate a number of operations in aparticular order, operations which are not order dependent may bereordered and other operations may be combined or broken out. While somereordering or other groupings are specifically mentioned, others will beapparent to those of ordinary skill in the art and so do not present anexhaustive list of alternatives. Moreover, it should be recognized thatthe stages could be implemented in hardware, firmware, software or anycombination thereof.

In the foregoing specification, the disclosure has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope as set forth in the following claims. Thespecification and drawings are, accordingly, to be regarded in anillustrative sense rather than a restrictive sense.

What is claimed is:
 1. A system, comprising: a radio frequencycommunication apparatus having an antenna and configured to operatewithin multiple frequency ranges in a field of wireless communication;and a device having a memory storing an identification number uniquelyidentifying the device among a plurality of devices for wirelesscommunication in the field with the radio frequency communicationdevice, the plurality of devices storing respective identificationnumbers; a device antenna having a single antenna structure resonant onthe multiple frequency ranges, and a circuit coupled with the deviceantenna and configured to use the single antenna structure tocommunicate, simultaneously over the multiple frequency ranges, with thecommunication apparatus according to different protocols; where eachprotocol of the different protocols uses a respective frequency range ofthe multiple frequency ranges.
 2. The system of claim 1, wherein theradio frequency communication apparatus includes multiple antennas, eachtuned to a different frequency range.
 3. The system of claim 1, whereinthe antenna of the radio frequency communication apparatus is amultiband resonant antenna.
 4. The system of claim 1, wherein the radiofrequency communication apparatus is configured to transmit power on atleast one frequency range to the device antenna.
 5. The system of claim1, wherein a first frequency range of the multiple frequency ranges isused for communication and a second frequency range of the multiplefrequency ranges is used to provide power to the device.
 6. The systemof claim 5, wherein the second frequency range used to provide power tothe device is lowest in frequency in the multiple frequency ranges. 7.The system of claim 1, wherein the multiple frequency ranges areselected to be non-harmonic, non-integer multiple, andnon-integer-fraction with each other in frequency.
 8. The system ofclaim 1, further comprising second radio frequency communicationapparatuses having antennas tuned to different frequency ranges tocommunicate with the device at the different frequency ranges accordingto respective protocols.
 9. A device, comprising: a memory storing anidentification number uniquely identifying the device among a pluralityof devices in a field of wireless communication; a radio frequencycommunication circuit; and an antenna coupled to the radio frequencycommunication circuit, the antenna having a single antenna structureresonant on multiple frequency ranges; wherein the radio frequencycommunication circuit is configured to use the single antenna structureto communicate with at least one communication apparatus according todifferent protocols simultaneously over the multiple frequency ranges;and wherein each protocol of the different protocols uses a respectivefrequency range of the multiple frequency ranges.
 10. The device ofclaim 9, wherein the antenna includes at least one filter to configurethe antenna to resonate within a particular frequency range.
 11. Thedevice of claim 9, wherein the antenna is one of: a dipole antenna, alog periodic dipole array antenna, a triband yagi antenna, quarter wavedipole antenna, a monopole antenna, and a whip antenna.
 12. The deviceof claim 9, wherein the antenna is configured to receives at least onepower transmission from the communication apparatus.
 13. The device ofclaim 9, wherein a first frequency range of the multiple frequencyranges of the multiple frequency ranges is used for communications and asecond frequency range of the multiple frequency ranges is used tosimultaneously receive power from the communication apparatus.
 14. Thedevice of claim 13, wherein the second frequency range used to providepower from the communication apparatus is lowest in frequency in themultiple frequency ranges.
 15. The device of claim 9, wherein themultiple frequency ranges are non-harmonic, non-integer multiple, andnon-integer fraction of each other in frequency.
 16. A method,comprising: receiving radio frequency signals transmitted usingdifferent protocols simultaneously over different frequency ranges of asingle antenna structure of an antenna coupled to a radio frequencydevice storing an identification number uniquely identifying the deviceamong a plurality of devices in a wireless communication field, thesingle antenna structure resonate on the different frequency ranges,each protocol of the different protocols using a respective frequencyrange of the different frequency ranges; and processing the radiofrequency signals according to the different protocols associated withthe multiple frequency ranges for simultaneously communication over themultiple frequency ranges.
 17. The method of claim 16, furthercomprising filtering the radio frequency signals within particularfrequency ranges.
 18. The method of claim 16, further comprisingpowering the device with at least one of the radio frequency signals.19. The method of claim 16, further comprising transmitting data fromthe device through the antenna to at least one communication apparatus.20. The method of claim 16, wherein a first frequency range of thedifferent frequency ranges is used for communications and a secondfrequency range of the different frequency ranges is used to receivepower in the device.